Quasi-Solid State Dye-Sensitized Solar Cells Based on the Novel Crosslinked Polymer Electrolyte

Abstract

A quasi-solid-state three-dimensionally crosslinked poly(citric acid-ethylene glycol)(PCE)/ LiI/I 2 polymer electrolyte has been prepared using biodegradable PCE synthesized via a crosslinking reaction between citric acid(CA)and oligo-polyethylene glycol(PEG)(average molecular weight Mw = 200,400,1000,2000)as a matrix.The molecular structure of the PCE matrix,micro-morphology of polymer electrolyte,and the state of conductive ion-pairs in the electrolyte were characterized by infrared(IR)spectrum, 1H nuclear magnetic resonance( 1H-NMR),and Raman spectroscopy,as well as scanning electron microscopy(SEM).The ionic diffusion coefficient and conductivity of polymer electrolytes and the output current-voltage(I-V)properties of the cells were investigated via linear sweep voltammetry.The results reveal that PEG molecular weights influence the mesh morphology and theabsorbent properties of the PCE matrix,which influences the polymer electrolyte ionic conductive performance and the photoelectric performance of the cells.As PEG molecular weights increased from 200,400,1000 to 2000,the PCE matrix mesh structure became looser,the liquid electrolyte uptake of the matrix increased,and the transition activation energies of I - 3 in the swollen PCE matrix decreased,which led to an increase in the electrolyte conductivity and the short circuit photocurrent densities of the cells accordingly.The photoelectric conversion efficiencies of the cells assembled by the four polymer electrolytes above were 3.26%,3.34%,4.26%,and 4.89%,respectively,under an incident light intensity of 60 mW·cm -2 .